1. Field of the Invention
The present invention relates to a channel estimation method and apparatus of a mobile communication system. More particularly, the present invention relates to a method and apparatus for estimating a channel efficiently through pilot subcarrier signal transformation and noise reduction in a mobile communication system.
2. Description of the Related Art
In Orthogonal Frequency Division Multiplexing (OFDM) systems, channel estimations are performed in a time frequency domain or a frequency domain. It is well-known in the art that the time domain channel estimation technique based on Discrete Fourier Transform (DFT) or Discrete Cosine Transform (DCT) is superior to the frequency domain channel estimation technique in performance under the same complexity. Channel estimation techniques based on DFT or DCT, according to the related art, require N-point DFT (DCT). Here, N is the total number of subcarriers for data and pilot or the total number of subcarriers for the data, pilot, and guard band.
In spite of its lower computation requirements, linear polarization has a large channel estimation error. The channel estimation error of the linear polarization technique causes degradation of a channel estimation performance, resulting in degradation of a system throughput. Meanwhile, a Minimum Mean-Square Error (MMSE) estimation guaranteeing an accurate channel requires previous statistical knowledge on the channel. The MMSE estimator also has high computational complexity of matrix inversion, resulting in difficulty of use. In order to implement the DFT (DCT)-based channel estimator according to the related art, N-point DFT (DCT) computations are required once or twice. Accordingly, complexity of the estimator mainly depends on an implementation of the N-point DFT (DCT). As described above, N is the total number of the subcarriers for data and pilot or the total number of the subcarriers for data, pilot, and guard band.
Mobile communication systems are developed to provide subscribers with voice communication services on the move. With the rapid advance of technologies, the mobile communication systems have evolved to support high speed data communication services as well as standard voice communication services. As N increases, both hardware implementation complexity and computation time increases.